The present disclosure relates to abrasive particles and a polishing slurry, and more particularly, to abrasive particles and a polishing slurry which can be used in the manufacturing process of semiconductors for chemical mechanical polishing to planarize dielectric layers, and to a method of fabricating the abrasive particles.
Chemical mechanical polishing (CMP) process is carried out by applying a slurry containing abrasive particles on a workpiece, and rotating a polishing pad attached to a polishing apparatus. The abrasive particles then mechanically polish the surface of the workpiece, while chemical substances contained in the slurry chemically reacts with the surface, thereby chemically removing the surface of the workpiece. Examples of such abrasive particles include silica (SiO2), ceria (CeO2), alumina (Al2O3), and titanium oxides (TiO2), and can be selectively used depending on a type of the workpiece.
On the other hand, in the manufacturing process of the NAND flash memory devices of fine design rules (for example, 19 or 16 nm), Shallow Trench Isolation (STI) process and CMP process are used. Here, the CMP process involves polishing a dielectric layer, namely a silicon dioxide layer, until a polysilicon layer is exposed. Also, in the manufacturing process of application processor (AP) of fine design rules (for example, 14 nm), silicon or silicon-germanium field effect transistors (FET) are manufactured, and the CMP process is used. Here, the CMP process involves polishing a dielectric layer, namely, a silicon dioxide layer, until a nitride layer is exposed.
The above CMP process involves polishing silicon oxide layers while having polysilicon layers or nitride layers as the polishing or etching stop layers, and utilizes the abrasive particles suitable for such uses. For example, ceria is used as the abrasive particles, and ceria can be fabricated by a dry process or a wet process. The dry-process ceria particles, due to constraints associated with the fabricating process, have crystal grains in an angular shape and a wide particle size distribution that inevitably lead to micro-scratches at the polishing stop layers when applied for the CMP process. On the other hand, the wet-process ceria particles have a narrow size distribution without larger particles of a secondary particle size, and have a poly-hedral structure, thus can lessen the occurrence of micro-scratches compared to the conventional dry-process ceria particles. However, the wet-process ceria particles are difficult to fabricate, and the problem of generating micro-scratches due to the sharp facets of its poly-hedral structure has not been resolved.
Also, as the design rule of various devices mentioned above decreases, the devices become more vulnerable to polishing scratches, damage, and the like. However, the ceria abrasive particles until now have a size of a few tens of nanometers and are poly-hedral shaped with sharp facets of the polyhedron. Consequently, the ceria abrasive particles continue to contribute to the problems of generating scratches, abrasions and pits on the surfaces of various devices being polished, or etching stop layers.
In U.S. Pat. No. 6,221,118 and No. 6,343,976, a method of forming ceria abrasive particles and a method of polishing wafers using the same are disclosed.